The flight of the boomerang has fascinated man for thousands of years. In this century it has attracted the attention of many scientific minds. Basically the flight is a circular path, similar to that of an airplane executing a banked turn.
The boomerang is thrown overhand with its plane in nearly vertical orientation accompanied by a snapping action to impart rotation. It flies in a circle because the upper wings, which are rotating into the wind, develop greater aerodynamic lift (due to their greater relative airspeed) than the lower wings which are rotating with the wind. This creates a banking moment which is converted by gyroscopic precession to a turn. There is a saying that the boomerang is the device "that can't be thrown away"--because it can't fly in a straight line.
It is well known that the earliest boomerangs were constructed of wood. Their planform was curved to form an arc or "L" shape which is often referred to as the Australian or aboriginal shape. Boomerangs of this shape have existed for several millenia.
A number of designs suitable for construction in thermoplastic have been patented. These designs often had three or more wings as opposed to the two wings of the aboriginal configuration. The benefit of more wings was that each of the wings could be shorter than those of the aboriginal design. These shorter wings were much better suited to the greater flexibility of thermoplastic materials--when compared to wood. Examples of such boomerang patents are:
U.S. Pat. No. 3,082,572 to Knox PA1 U.S. Pat. No. 3,403,910 to Claycomb PA1 U.S. Pat. No. 3,955,817 to Davis PA1 U.S. Pat. No. 862,094 to Morton PA1 U.S. Pat. No. 2,234,022 to Prause PA1 US Magazine, June 20,1983, photograph on page 38. PA1 U.S. Pat. No. 4,203,249 to Bohm PA1 U.S. Pat. No. 4,307,535 to Martin PA1 a. has a long-range flight pattern like a classic Australian or tournament-quality boomerang, PA1 b. can be caught easily and safely with one hand upon return, PA1 c. can be mass produced from thermoplastic materials.
Claycomb uses three wings while Knox and Davis each employ a greater number of wings, surrounded by an outer hoop.
Other devices of relevance are:
Morton, in his FIG. 5, discloses a device with four wings joined together at a small ring-shaped hub. Prause discloses a three winged boomerang wherein the wings join together in the center in a manner which produces a small triangular central openings. US Magazine shows a six-winged boomerang which resembles the Morton device, except for its greater number of wings.
These boomerangs fly in a relatively small diameter flight pattern when compared to their aboriginal ancestors. Because of this small flight pattern, their performance has always been of limited interest to an experienced boomeranger who seeks the challenge and excitement of a long range flight pattern.
The experienced boomeranger also takes pride in catching a boomerang with one hand when it returns. Though somewhat dangerous there are formal boomerang competitions which include one-handed catching. While this is possible with the aboriginal shape which is caught (very carefully) in its center, it is impractical with multi-winged designs such as those listed above. Two other aerial devices, both of "Flying Saucer" classification are noted here:
Although these devices are classified as "flying saucers" rather than boomerangs, their inventors make reference to "boomerang" behavior. Thus they are included here.
It has been found that devices like those disclosed by Bohm and Martin can be made to return by throwing them upwards at an angle of about 45 degrees and into a strong wind so that it may slide back down to the thrower, but they are not capable of executing the flight of a boomerang--which is a full circle of flight at a relatively constant altitude. The Bohm and Martin discs are not be capable of executing the required maneuvers in a boomerang tournament and thus are not commercialy valuable in that market.